Semiconductor device and method for manufacturing the same

ABSTRACT

Semiconductor device and method for manufacturing the same prevent the spread of a tungsten film out of an opening portion of a contact hole when the tungsten is grown in the contact hole and avoid inferior wiring shape and inter-wiring shirt-circuit. After a titanium/titanium nitride film is formed along an inner surface of the contact hole, a photo-resist film is applied. Then, the photo-resist film is etched away until a distance from an upper end of the contact hole to the surface of photo-resist film is not smaller than one-half of a width of the contact hole when the titanium/titanium nitride film is formed. After the titanium/titanium nitride film is etched by using the photo-resist as a mask, the photo-resist film is removed and a tungsten layer is selectively grown by using the titanium/titanium nitride film as a seed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to semiconductor device and methodfor manufacturing the same by selectively forming a metal thin film on asemiconductor substrate as a contact plug.

[0003] 2. Description of the Related Art

[0004] As the high integration and microminiaturization of asemiconductor device have recently been promoted, a multi-layer wiringtechnology becomes essential. In order to accomplish the multi-layerwiring structure, a device region of a MOS or bipolar transistor and themetal wire, or a plurality of metal wires must be interconnected throughan insulation film.

[0005] In the past, in order to conduct such wiring, a desired contacthole is formed in the insulation film and a metal wire is buried in thecontact hole simultaneously with the formation of an upper layer metalwire. However, recently, a diameter of the contact hole is in the orderof sub-micron and an aspect ratio of the contact hole formed in theinsulation layer is larger than unity. The aspect ratio is defined as aratio of a depth to a diameter of the opening. As the aspect ratioincreases, the metal wire does not fully go into the contact hole andpositive connection may not be attained.

[0006] In order to avoid the above problem, a tungsten selective growthmethod as disclosed in JP-A-4-25159 has been proposed.

[0007] The wiring formation method of the above patent application isbriefly explained. First, an insulation film is formed on asemiconductor substrate and a contact hole is formed in the insulationfilm. A relatively thin metal silicide film is formed on an entiresurface of a semiconductor substrate as a seed for selective growth andthen a photo-resist film is formed on the semiconductor substrate, andthen the photo-resist film and the metal silicide film are etched backto keep the metal silicide film only within the contact hole. After thephoto-resist film remaining in the contact hole is removed, a tungstenfilm is selectively grown in the contact hole by using the metalsilicide as the seed. Thus, a wiring layer including the tungsten filmwhich is fully fills the contact hole is formed. Since the tungsten filmis hard to be formed on the insulation film, the metal silicide film isformed as the seed for the selective growth.

[0008] However, in the method of the above patent publication, since themetal silicide film remains at the opening portion of the contact hole(an upper edge of the contact hole), when the tungsten film isselectively grown in the contact hole by using the metal silicide filmas the seed and the contact hole is filled with the tungsten film, thetungsten film also grows from the opening portion of the contact holeand the tungsten film spreads out of the opening portion of the contacthole. As a result, when the metal wiring is formed on the tungsten filmspread out of the opening portion of the contact hole, inferior wiringshape or inter-wiring short-circuit may occur.

[0009] JP-A-5-283536 discloses a manufacturing method which preventstitanium/titanium nitride on an inner wall of a contact hole from beingetched by misalignment when a conductive film formed on the contact holeis etched to form the wiring.

[0010] This method is briefly explained. After the titanium/titaniumnitride is sputtered on the inner wall of the contact hole formed in aninterlayer insulation film on a semiconductor substrate, tungsten isvapor-grown to fill the contact hole. Then, the surface of theinterlayer insulation film is exposed by dry etching and only thetitanium/titanium nitride is selectively etched to form a groove. Aftera silicon oxide film is vapor-grown to fill the groove, the surface ofthe tungsten is exposed by dry etching and a conductive film issputtered thereon. The conductive film is dry etched by using aphoto-resist as a mask to complete the wiring.

[0011] In this method, however, an area of the contact is substantiallyreduced by the thickness of the silicon oxide film and a higher accuracyis required in positioning when the wiring is formed on the contacthole. On the other hand, if the contact hole is enlarged accordingly, itis against the high integration of the semiconductor device. Further, aprocess to vapor grow the silicon oxide and a process to expose thesurface of the tungsten by the dry etching are required and it makes themanufacturing process of the semiconductor device complex.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide semiconductordevice and method for manufacturing the same which do not make amanufacturing process of the semiconductor device complex and do notcause inferior wiring shape or short-circuit of wiring when thesemiconductor devices are highly integrated.

[0013] In order to achieve the above object, according to the presentinvention, the method for manufacturing a semiconductor device having aninsulation film comprises the steps of forming a contact hole in theinsulation film, forming a first conductive film on an entire surfaceincluding an inner surface of the contact hole, applying a film forfilling the contact hole, etching the applied film until a distance froman opening portion of the contact hole to a surface of the applied filmis not smaller than one-half of a width of the contact hole less twiceof a thickness of the first conductive film while the applied filmremains at a bottom of the contact hole, etching the first conductivefilm by using the applied film as a mask, removing the remaining appliedfilm, and selectively growing a second conductive film to fill thecontact hole by using the first conductive film remaining on the innersurface of the contact hole as a seed for the selective growth.

[0014] According to the present invention, the semiconductor devicecomprises a semiconductor substrate, an insulation film formed on saidsemiconductor substrate and having a contact hole, a first conductivefilm formed on an inner surface of said contact hole, a distance from anopening portion of said contact hole to an upper end of said firstconductive film being not smaller than one-half of a width of saidcontact hole less twice of a thickness of said first conductive film anda second conductive film formed on said first conductive film to fillsaid contact hole.

[0015] In accordance with the present invention, in order to etch awaythe first conductive film (barrier layer) which serves as a seed for theselective growth of the second conductive film (plug) above the contacthole until a predetermined condition is met, the filling of the contacthole is completed before the second conductive film spreads out of theupper edge of the contact hole when the second conductive film isselectively grown in the contact hole.

[0016] When a plurality of contact holes of different widths arepresent, the first conductive film is etched away above the contact holesuch that the predetermined condition is met for the widest contacthole. Thus, when the second conductive film is grown in the contacthole, the second conductive film does not spread out of the upper edgeof any of the contact holes.

[0017] Further, since the first or second conductive film is fullyfilled in the contact hole, the entire area may be used as the contactand the high integration of the semiconductor device is not prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIGS. 1A-1C show sectional views for illustrating a principle ofthe semiconductor device and the manufacturing method thereof accordingto the present invention; and

[0019] FIGS. 2A-2E show sectional views for illustrating sequentialprocesses of the semiconductor device and the manufacturing methodthereof according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] First, referring to FIGS. 1A-1C, a principle of the semiconductordevice and the manufacturing method thereof according to the presentinvention is explained.

[0021] In FIG. 1A, distances from opening portions (upper ends) ofcontact holes 21 and 22 to the tops of a barrier layer 23, respectively,are M for the narrow contact hole 21 and the wider contact hole 22. Thenarrower contact hole 21 has a width X when the barrier layer 23 isformed, and the distance M from the upper end of the contact hole 21 tothe top of the barrier layer 23 is larger than a length L which isone-half of the width X. The wider contact hole 22 has a width Y whenthe barrier layer 23 is formed, the distance M from the upper end of thecontact hole 22 to the top of the barrier layer 23 is larger than alength N which is one-half of the width Y.

[0022] As shown in FIG. 1B, when plugs 24 are partially formed in thecontact holes 21 and 22, the barrier layer 23 serves as a seed for theselective growth of the plug 24, and since the growth rates are same,distances from the upper ends of the contact holes 21 and 22 to the topof the plug 24, respectively, are P. Since the contact hole 21 isnarrower than the contact hole 22, the plugs 24 grown from the barrierlayers 23 on the opposite sides of the connection layer 21 contacttogether and are integrated around a center before the contact hole 21is entirely filled. Thereafter, the plug 24 growths upward substantiallyuniformly for the contact hole 21.

[0023] As shown in FIG. 1C, as to the contact hole 22, the plugs grownfrom the barrier layers 23 on the opposite sides contact each other andare integrated around the center when the contact hole 22 is fullyfilled. At this time, the plug 24 of the contact hole 21 also fullyfills the contact hole 21, and the plug 24 does not spread out of theupper end of the contact hole 21 or 22.

[0024] When a plurality of contact holes 21 and 22 of different widthsare present, the distance from the top of the barrier layer 23 to theopening portion (upper end) of the contact hole is set to be larger thanthe predetermined length for the widest contact hole 22 so that the plug24 does not spread out of the opening portion (upper end) of any of thecontact holes 21 and 22 when the plug 24 is selectively grown in thecontact holes 21 and 22.

[0025] Referring to FIGS. 2A-2E, an embodiment of the present inventionis explained in detail.

[0026] FIGS. 2A-2E show sectional views for illustrating processes ofthe semiconductor device and the manufacturing method thereof accordingto the present invention. As shown in FIG. 2A, a gate electrode (notshown) of a MOS transistor comprising a poly-crystalline silicon filmincluding impurities is formed in a device forming area of asemiconductor substrate 1 through a gate insulation layer (not shown),and then a pair of impurity layers (one of which is shown by 2 and theother is not shown in the sectional views of FIG. 2A) which serve as asource and a drain are formed by ion implantation into a surface of thesemiconductor substrate 1 on the opposite sides of the gate electrode.Then, an interlayer insulation film 3 comprising an oxide silicon filmor a BPSG (boro-phospho silicate glass) film, a PSG (phospho-silicateglass) film or a BSG (boro-silicate glass) film is formed on an entiresurface of the semiconductor substrate 1 and a contact hole (not shown)which extends through the interlayer insulation film 3 and has otherimpurity doped layer (not shown) as a bottom is formed and then a metalwiring layer 4 which fills an inner surface of the contact hole ispattern-formed.

[0027] Then, an impurity containing fusing glass such as a BPSG film, aPSG film or a BSG film is formed on the semiconductor substrate 1, and asurface is flattened. A contact hole 31 which extends through theimpurity containing fusing glass 5 and the interlayer insulation film 3and has the impurity doped layer 2 as a bottom is formed, and a contacthole 32 which extends through the impurity containing fusing glass 5 andhas the metal wiring layer 4 as a bottom is formed. In those two contactholes 31 and 32, the depth of the contact hole 31 is deeper than thedepth of the contact hole 32 by the thickness of the interlayerinsulation film 3 and the metal wiring layer 4. A diameter of thecontact hole 31 is 0.6 μm (600 nm) and a diameter of the contact hole 32is 0.4 μm (400 nm). Then, a titanium film and a titanium nitride filmare sequentially formed on the surface of the semiconductor substrate 1including the contact holes 31 and 32 by a sputtering method to form atitanium/titanium nitride stacked layer 6 having a film thickness ofapproximately 100 nm at the upper surface. The titanium/titanium nitridestacked thin film 6 is formed along the unevenness of the contact holesto prevent the contact holes 31 and 32 from being filled. Thereafter, aphoto-resist film 7 is applied to the film thickness of approximately1.5 μm as a flattening layer.

[0028] As shown in FIG. 2B, after the photo-resist layer is baked atapproximately 200° C., the photo-resist layer 7 is etched back by oxygenplasma to an upper surface of the impurity containing fusing glass 5 andthe inside of the contact holes 31 and 32. It is designed such that thephoto-resist film 7 remains at the bottoms of the contact holes 31 and32 and the distance from the upper end of the contact hole 31 to thesurface of the photo-resist film 7 is not smaller than one-half of thewidth of the connection layer when the titanium/titanium nitride stackedlayer 6 is formed, and preferably ⅝˜⅞and more preferably approximately¾when variations in the manufacturing process are taken intoconsideration. Thus, for the contact hole 32 which is narrower than thecontact hole 31, the distance from the upper end of the contact hole 32to the surface of the photo-resist film 7 is naturally not smaller thanone-half of the width of the contact hole 32 when the titanium/titaniumnitride stacked thin film 6 is formed. In the present embodiment, sincethe thickness of the titanium/titanium nitride stacked thin films 6 onthe sides of the contact holes 31 and 32 is 50 nm, the etching is madesuch that the distance (depth) from the upper ends of the contact holes31 and 32 to the surface of the photo-resist film 7 is not smaller than(600− 50×2)/2=250 nm, and preferably 400 nm.

[0029] Thereafter, the titanium/titanium nitride stacked thin film 6 onthe impurity containing fusing glass 5 and on the inner surfaces of thecontact holes 31 and 32 which are not covered by the photo-resist film 7is removed by ECR (electron cyclotron resonance) plasma in chlorineenvironment. Accordingly, the distance (depth) from the upper ends ofthe contact holes 31 and 32 to the top of the titanium/titanium nitridestacked thin film 6 is also 400 nm.

[0030] The etching process of the photo-resist film 7 and the etchingprocess of the titanium/titanium nitride stacked thin film 6 describedabove may be replaced as follows.

[0031] After the photo-resist film 7 is baked at approximately 200° C.,the photo-resist film 7 is etched back to the upper surface of the glass5 by oxygen plasma, and then the photo-resist layer 7 in the contactholes 31 and 32 and the titanium/titanium nitride stacked thin film 6 onthe upper surface of the glass 5 and on the inner surfaces of thecontact holes 31 and 32 are etched away. The photo-resist film 7 and thetitanium/titanium nitride stacked thin film 6 are removed to thesubstantially same depth because the etching rates thereof in thechlorine environment are substantially same.

[0032] Further, by making use of the fact that the etching rates of thephoto-resist film 7 and the titanium/titanium nitride stacked thin film6 in the chlorine environment are substantially same, after thephoto-resist film 7 is applied as shown in FIG. 2A, the photo-resistfilm 7 and the titanium/titanium nitride stacked thin film 6 may beetched to the inside of the contact holes 31 and 32 by the ECR plasma inthe chlorine environment.

[0033] In those case, the distance from the upper end of the contacthole 31 to the surface of the photo-resist film 7 is made to be withinthe range described above.

[0034] Next, as shown in FIG. 2C, the photo-resist layer 7 serving asflattening layer and remaining in the contact holes 31 and 32 iscompletely removed by ashing or organic cleaning. Thus, thetitanium/titanium nitride stacked thin film 6 remaining on the bottomsurfaces and portions of sides of the contact holes 31 and 32 isexposed.

[0035] As shown in FIG. 2D, a tungsten seed (not shown) is selectivelyand thinly grown on only the titanium/titanium nitride stacked thin film6 remaining in the contact holes 31 and 32 by using a tungsten CVDdevice, and a tungsten layer 8 is selectively grown only in the contactholes 31 and 32 by using the titanium/titanium nitride stacked thin film6 as the seed for the selective growth at 75 sccm of tungstenhexa-fluoride, 450 sccm of hydrogen, temperature of 450° C. and pressureof 80 Torr, where the “sccm” is a unit of flow rate representing avolume (cc) flowing in one minute under a standard condition.

[0036] The tungsten layer 8 is grown from the surface of thetitanium/titanium nitride stacked thin film 6 and completely fills thecontact holes 31 and 32. Since the depth of the titanium/titaniumnitride stacked thin film 6 is defined as described above, both thecontact holes 31 and 32 may be simultaneously filled before the top ofthe tungsten layer 8 grows beyond the openings of the contact holes 31and 32. Namely, by properly selecting the growth time of the tungstenlayer 8, the tungsten layer does not spread out of the contact holes 31and 32 and the tungsten layer 8 may be formed only in the contact holes31 and 32.

[0037] Further, since the diameter (width) of the contact hole 31 is400−50×2=300 nm when the titanium/titanium nitride stacked thin film 6is formed and it is smaller than that of the contact hole 31, it isfilled with the tungsten layer to the center before the contact hole 31is completely filled by the tungsten layer 8. However, since thetitanium/titanium nitride stacked thin film 6 is recessed byapproximately 0.4 μm (400 nm), a gap of 0.4−0.3/2=0.25 μm remains atthis moment between the opening portion of the contact hole 32 and thetop of the tungsten layer 8. Further, since the recess depth from theopening portion of the titanium/titanium nitride stacked thin film 6 ofthe contact hole 32 is same as that of the contact hole 31, the depthfrom the top of the tungsten layer 8 is also 0.25 μm. Thereafter, whenthe tungsten layer 8 has been grown to 0.1 μm, the contact hole 31 isfilled to the center and the tungsten layer 8 is further grown by 0.15μm to fill both the contact holes 31 and 32.

[0038] As shown in FIG. 2E, a stacked metal wiring 11 comprising atitanium film 9 and an aluminum alloy 10 is pattern-formed. By thoseprocesses, the upper and lower wirings are connected with a goodcharacteristic and without short-circuit.

[0039] In the present embodiment, a semiconductor device having theconnection between the substrate and the first layer metal wiring andthe connection between the first layer metal wiring and the second layermetal wiring has been shown although the present invention may be usedfor any other connection between wiring layers.

[0040] In the present embodiment, although the titanium/titanium nitridestacked thin film 6 is used as the underlying layer to grow the tungstenlayer 8, other thin film material may be used for growing the tungstenlayer 8. For example, instead of the titanium/titanium nitride stackedthin film 6, a tungsten film, a tungsten silicide film, a molybdenumfilm, a molybdenum silicide film, a poly-crystalline silicon film, anamorphous silicon film or a germanium film may be used. Further, a metalsilicide film, a metal film, a nitride conductive film, a silicate, asemiconductor thin film or silicon (amorphous silicon orpoly-crystalline silicon) which allows the selective growth of thetungsten layer 8 may be used.

[0041] In the present embodiment, the tungsten layer 8 is used to fillthe contact holes although a metal film which allows the selectivegrowth by using the underlying film as the seed, for example, analuminum film or an aluminum alloy may be selectively grown instead ofthe tungsten layer 8.

[0042] The film thicknesses and the forming methods are not limited tothose described in the embodiment and various modifications may be madeby those skilled in the art within the scope of the technical concept ofthe present invention.

[0043] In accordance with the present invention, the plug such as thetungsten does not spread out of the opening portion of the contact holewhen the plug is selectively grown in the contact hole and the inferiorwiring shape and the inter-wiring short-circuit are avoided.

1. A method for manufacturing a semiconductor device having aninsulation film, comprising the steps of: forming a contact hole in saidinsulation film; forming a first conductive film on a surface of saidsemiconductor device including an inner surface of said contact hole;applying a film for filling said contact hole; etching said applied filmuntil a distance from an opening portion of said contact hole to asurface of said applied film becomes not smaller than one-half of awidth of said contact hole less twice of a thickness of said firstconductive film while said applied film remains at a bottom of saidcontact hole; etching said first conductive film by using said appliedfilm as a mask; removing said remaining applied film; and selectivelygrowing a second conductive film to fill said contact hole by using saidfirst conductive film remaining on the inner surface of said contacthole as a seed for selective growth.
 2. A method for manufacturing asemiconductor device having an insulation film, comprising the steps of:forming a contact hole in said insulation film; forming a firstconductive film on a surface of said semiconductor device including aninner surface of said contact hole; applying a film for filling saidcontact hole; etching said applied film until said first conductive filmis appeared; etching said applied film and said first conductive filmuntil a distance from an opening portion of said contact hole to thesurface of said applied film and the end of said first conductive filmbecomes not smaller than one-half of a width of said contact hole lesstwice of a thickness of said first conductive film while said appliedfilm and said first conductive film remain at a bottom of the contacthole; removing said remaining applied film; and selectively growing asecond conductive film to fill said contact hole by using said firstconductive film remaining on the inner surface of said contact hole as aseed for selective growth.
 3. A method for manufacturing a semiconductordevice having an insulation film, comprising the steps of: forming acontact hole in said insulation film; forming a first conductive film ona surface of said semiconductor device including an inner surface ofsaid contact hole; applying a film for filling said contact hole;etching said applied film and said first conductive film until adistance from an opening portion of said contact hole to the surface ofsaid applied film and the end of said first conductive film becomes notsmaller than one-half of a width of said contact hole less twice of athickness of said first conductive film while said applied film and saidfirst conductive film remain at a bottom of said contact hole; removingsaid remaining applied film; and selectively growing a second conductivefilm to fill said contact hole by using said first conductive filmremaining on the inner surface of said contact hole as a seed forselective growth.
 4. A method for manufacturing a semiconductor deviceaccording to claim 1 , wherein: said step of forming a contact holeincludes a step of forming a plurality of contact holes having differentwidths; and said step of etching said applied film includes a step ofetching said applied film until a distance from the opening portion ofsaid each contact hole to the surface of said applied film becomes notsmaller than one-half of the value left by subtracting twice of thethickness of said first conductive film from the width of the contacthole having the largest width.
 5. A method for manufacturing asemiconductor device according to claim 2 , wherein: said step offorming a contact hole includes a step of forming a plurality of contactholes having different widths; and said step of etching said appliedfilm and said first conductive film includes a step of etching saidapplied film and said first conductive film until a distance from theopening portion of said each contact hole to the surface of said appliedfilm and the end of said first conductive film becomes not smaller thanone-half of the value left by subtracting twice of the thickness of saidfirst conductive film from the width of the contact hole having thelargest width.
 6. A method for manufacturing a semiconductor deviceaccording to claim 3 , wherein: said step of forming a contact holeincludes a step of forming a plurality of contact holes having differentwidths; and said step of etching said applied film and said firstconductive film includes a step of etching said applied film and saidfirst conductive film until a distance from the opening portion of saideach contact hole to the surface of said applied film and the end ofsaid first conductive film becomes not smaller than one-half of thevalue left by subtracting twice of the thickness of said firstconductive film from the width of the contact hole having the largestwidth.
 7. A method for manufacturing a semiconductor device according toclaim 1 , wherein: said first conductive film includes one of atitanium/titanium nitride stacked film, a tungsten film, a tungstensilicide film, a molybdenum film, a molybdenum silicide film, apoly-crystalline silicon film, an amorphous silicon film and a germaniumfilm; and said second conductive film includes one of a tungsten film,an aluminum film and an aluminum alloy film.
 8. A method formanufacturing a semiconductor device according to claim 2 , wherein:said first conductive film includes one of a titanium/titanium nitridestacked film, a tungsten film, a tungsten silicide film, a molybdenumfilm, a molybdenum silicide film, a poly-crystalline silicon film, anamorphous silicon film and a germanium film; and said second conductivefilm includes one of a tungsten film, an aluminum film and an aluminumalloy film.
 9. A method for manufacturing a semiconductor deviceaccording to claim 3 , wherein: said first conductive film includes oneof a titanium/titanium nitride stacked film, a tungsten film, a tungstensilicide film, a molybdenum film, a molybdenum silicide film, apoly-crystalline silicon film, an amorphous silicon film and a germaniumfilm; and said second conductive film includes one of a tungsten film,an aluminum film and an aluminum alloy film.
 10. A method formanufacturing a semiconductor device according to claim 1 furthercomprising the step of forming on said insulation film a thirdconductive film to be connected to said second conductive film.
 11. Amethod for manufacturing a semiconductor device according to claim 2further comprising the step of forming on said insulation film a thirdconductive film to be connected to said second conductive film.
 12. Amethod for manufacturing a semiconductor device according to claim 3further comprising the step of forming on said insulation film a thirdconductive film to be connected to said second conductive film.
 13. Amethod for manufacturing a semiconductor device according to claim 2 ,wherein: said step of etching said applied film includes a step ofetching said applied film by oxygen plasma; and said step of etchingsaid applied film and said first conductive film includes a step ofetching said applied film and said first conductive film by ECR(electron cyclotron resonance) plasma in chlorine environment.
 14. Amethod for manufacturing a semiconductor device according to claim 3wherein said step of etching said applied film and said first conductivefilm includes a step of etching said applied film and said firstconductive film by ECR (electron cyclotron resonance) plasma in chlorineenvironment.
 15. A semiconductor device comprising: a semiconductorsubstrate; an insulation film formed on said semiconductor substrate andhaving a contact hole; a first conductive film formed on an innersurface of said contact hole, a distance from an opening portion of saidcontact hole to the end of said first conductive film being not smallerthan one-half of a width of said contact hole less twice of a thicknessof said first conductive film; and a second conductive film formed onsaid first conductive film to fill said contact hole.
 16. Asemiconductor device according to claim 15 , wherein: said insulationfilm includes a first insulation film and a second insulation film; saidfirst insulation film includes one of a silicon oxide film, a BPSG(boro-phospho silicate glass) film, a PSG (phospho-silicate glass) filmand a BSG (boro-silicate glass) film; and said second insulation filmincludes one of a BPSG film, a PSG film and a BSG film.
 17. Asemiconductor device comprising: a semiconductor substrate; a firstinsulation film formed on said semiconductor substrate; a firstconductive film formed on said first insulation film; a secondinsulation film formed on said first conductive film and having acontact hole; a second conductive film formed on an inner surface ofsaid contact hole, a distance from an opening portion of said contacthole to the end of said second conductive film being not smaller thanone-half of a width of said contact hole less twice of a thickness ofsaid second conductive film; and a third conductive film formed on saidsecond conductive film to fill said contact hole.
 18. A semiconductordevice according to claim 17 , wherein: said first insulation filmincludes one of a silicon oxide film, a BPSG (boro-phospho silicateglass) film, a PSG (phospho-silicate glass) film and a BSG(boro-silicate glass) film; and said second insulation film includes oneof a BPSG film, a PSG film and a BSG film.
 19. A semiconductor deviceaccording to claim 15 , wherein: said first conductive film includes oneof a titanium/titanium nitride stacked film, a tungsten film, a tungstensilicide film, a molybdenum film, a molybdenum silicide film, apoly-crystalline silicon film, an amorphous silicon film and a germaniumfilm; and said second conductive film includes one of a tungsten film,an aluminum film and an aluminum alloy film.
 20. A semiconductor deviceaccording to claim 17 , wherein: said second conductive film includesone of a titanium/titanium nitride stacked film, a tungsten film, atungsten silicide film, a molybdenum film, a molybdenum silicide film, apoly-crystalline silicon film, an amorphous silicon film and a germaniumfilm; and said third conductive film includes one of a tungsten film, analuminum film and an aluminum alloy film.
 21. A semiconductor deviceaccording to claim 15 further comprising a third conductive film formedon said insulation film and connected to said second conductive film.22. A semiconductor device according to claim 17 further comprising afourth conductive film formed on said second insulation film andconnected to said third conductive film.